1. Field of the Invention
The invention relates to a technology for controlling a plurality of actuators in an integrated manner so as to perform a plurality of kinds of vehicle motion controls on a motor vehicle.
2. Description of Related Art
In recent years, there is an increasing tendency to install many kinds of motion control devices for controlling movements of the vehicle on the same vehicle. However, the effects achieved by the motion control devices of different kinds do not necessarily appear in the vehicle independently of each other, but may interfere with one another. When the development of the vehicle involves installation of the plural kinds of motion control devices on the vehicle, therefore, it is important to ensure sufficient cooperation (or coaction) and coordination of these motion control devices.
For example, when a plurality of kinds of motion control devices need to be mounted in the same vehicle at a certain development stage of the vehicle, the motion control devices may be correlated or coordinated with each other in a supplemental or additional way after the individual control devices were developed independently of each other.
However, the development of the vehicle with the different kinds of the motion control devices as described above requires a lot of efforts and a long period of time for achieving correlation and coordination among the motion control devices.
As an example, a plurality of different kinds of motion control devices are installed on the vehicle such that these motion control devices share the same actuator or actuators. With this arrangement, if the motion control devices need to operate the same actuator(s) at the same time, a problem of conflict arises between controls by the different motion control devices.
It is difficult to ideally solve the above problem if the correlation/coordination of the motion control devices is established in a supplemental or additional way after the individual motion control devices were developed independently of each other, as described above. In some actual cases, the problem is solved by selecting one or more of the motion control devices to be given priority over the other control devices, and permitting the selected motion control device(s) to exclusively control the corresponding actuator(s).
In the meantime, U.S. Pat. No. 5,351,776 discloses a known example of a technology for controlling the vehicle movements in an integrated manner, for the purpose of shortening the development time of the vehicle as a whole, and improving the reliability and availability of the vehicle as well as making maintenance of the vehicle easier.
In the known example, an overall system consisting of the driver and the vehicle is constructed by a plurality of elements that are arranged in the form of a hierarchy having a plurality of hierarchical levels between the driver and actuators. When a request or intention of the driver is translated into a corresponding operating performance of the vehicle, the performance required from an upper-level element for a lower-level element is transmitted from the upper-level element to the lower-level element.
In the known example, while the above-described system is constructed in the hierarchical form in accordance with the relationship of components on the hardware configuration, the software configuration adapted for carrying out the plurality of kinds of motion controls does not necessarily have an appropriate hierarchical arrangement. This situation will be described below in greater detail.
As is understood from U.S. Pat. No. 5,351,776, control functions, in particular, control functions of the coordinating elements 12, 18 and 24, are realized in the form of program structures of the master controller 100. Namely, the control functions of these elements are implemented by executing programs in the master controller 100. The coordinating element 12 serves to translate a request of the driver into a target value, and the coordinating element 18 converts the target value received from the coordinating element 12 into vehicle wheel torque. Thus, the coordinating elements 12, 18 form a hierarchical structure.
On the other hand, the coordinating element 24 transmits a signal for realizing the engine torque received from the next higher element 22 to the actuator element 28 for controlling the intake air quantity of the engine, actuator element 30 for controlling the fuel injection quantity of the engine, and the actuator element 32 for controlling the ignition timing of the engine. Since the coordinating element 24 is subordinated only to the next higher-level element 22, but not to the above-described coordinating elements 12 and 18, the coordinating element 24 and the coordinating elements 12 and 18 do not form a hierarchical structure.
To make the software configuration form a hierarchical structure in a true sense, a plurality of processing units in the software configuration need to be independent of each other. “Independent” in this context means that a program of each processing unit can be executed by a computer without depending upon a program of another processing unit. Namely, the program to be executed by the computer in each processing unit needs to be a self-complete program that is completed by itself, namely, a module.
The above-identified U.S. Patent does not disclose the hierarchical structure of the software structure, independent processing units and modularization as described above.
Referring to FIG. 1 of U.S. Pat. No. 5,351,776, it may be proposed in this patent to classify and arrange a plurality of elements of the system in a hierarchical form merely in accordance with the relationship as to which of the elements belongs to or is subordinate to which of the elements, without telling whether the elements are hardware elements or software elements. However, the above U.S. Patent does not mention a technology for adequately arranging the software configuration of the system in hierarchical form.
To adequately arrange the software configuration in hierarchical form, it is necessary to fractionize necessary processing contents, thereby to improve the execution efficiency of the software configuration as a whole.
In sum, in the known example as described above, there is still room for improvement in the software configuration for executing a plurality of kinds of motion controls in the same vehicle in an integrated manner. With such an improvement in the software configuration, the technology for controlling a plurality of actuators in an integrated manner for controlling the movements of the vehicle will be established for use in actual applications.
It is therefore an object of the invention to adequately establish a hierarchical structure of the software configuration of a system that controls a plurality of actuators for executing a plurality of kinds of motion controls in a vehicle in an integrated manner, and to optimize the hierarchical structure in terms of applicability.